Diastereoselective Synthesis of Dibenzo[<i>b</i>,<i>d</i>]azepines by Pd(II)-Catalyzed [5 + 2] Annulation of <i>o</i>‑Arylanilines with Dienes

An efficient method for the construction of dibenzo­[<i>b</i>,<i>d</i>]­azepines containing two distinct stereogenic elements in a highly diastereoselective fashion is described. The key of the [5 + 2] reaction is to form a π-allylpalladium species through sequential C–H activation and regiospecific migratory insertion of the diene. This observation contrasts with the behavior of 1,2-alkenes that generally underwent direct alkenylation via β-hydride elimination